A Fresnel liquid crystal lens needs to allow significant phase change of liquid crystals within an extremely small space, so that the Fresnel liquid crystal lens can simulate the phase delay characteristics of an ideal Fresnel lens more accurately.
As shown in FIG. 1, a phase delay curve 12 of the ideal Fresnel lens is steep at a position P having a maximum change in phase delay, while a phase delay curve 13 stimulated by the Fresnel liquid crystal lens is usually mild at a position E having a maximum change in phase delay.
At present, to make the phase delay curve of the ideal Fresnel lens simulated by the Fresnel liquid crystal lens have higher level of simulation, that is, to make the liquid crystal phase delay curve simulated by the Fresnel liquid crystal lens more close to the phase delay curve of the ideal Fresnel lens, one of the solutions is to provide four layers of electrode structures on a substrate of a liquid crystal cell of a Fresnel liquid crystal lens, and by virtue of an electric field formed by the four layers of electrode structures, the liquid crystal phase delay curve simulated by the Fresnel liquid crystal lens is more close to the phase delay curve of the ideal Fresnel lens.
Due to the four layers of electrode structures, the manufacturing process of the Fresnel liquid crystal lens becomes complex and the allowable error of the four layers of electrode structures during the manufacturing process is small. As a result, it is difficult to manufacture a Fresnel liquid crystal lens of the four layers of electrode structures in some extent.
Another solution is to provide a polymer layer of a specific shape on the liquid crystal layer of the Fresnel liquid crystal lens, so as to reduce the space required by large change in phase difference generated by liquid crystals. However, as the refractive index of the polymer layer is different from that of the liquid crystals, it is likely to cause local refraction. As a result, when the Fresnel liquid crystal lens is in a non-lens working mode, the local refraction is likely to cause unclear light transmittance of the Fresnel liquid crystal lens, and the normal function of the Fresnel liquid crystal lens is influenced.